1. Field of the Invention
The present invention relates to preparation of microparticles. More particularly, the present invention relates to a method and an apparatus for preparing microparticles using in-line solvent extraction.
2. Related Art
A variety of methods is known by which compounds can be encapsulated in the form of microparticles. It is particularly advantageous to encapsulate a biologically active or pharmaceutically active agent within a biocompatible, biodegradable wall forming material (e.g., a polymer) to provide sustained or delayed release of drugs or other active agents. In these methods, the material to be encapsulated (drugs or other active agents) is generally dissolved, dispersed, or emulsified, using stirrers, agitators, or other dynamic mixing techniques, in a solvent containing the wall forming material. Solvent is then removed from the microparticles and thereafter the microparticle product is obtained.
Development of a microencapsulation process suitable for commercial scale production typically requires scaling up, by multiple factors, a laboratory scale process and/or a pilot scale process. The scaled-up process will almost always require larger piping and higher flow rates, particularly when the scale factor is very large or if it is desired or necessary to keep process transfer times similar to the smaller scale processes. Scale-up into new, larger equipment is often unpredicatable and achieved in large measure through trial and error. However, the economic costs of large-scale trial and error experiments can be prohibitive.
One approach to aiding the scale-up process is to use a static mixer to form an emulsion, as disclosed in U.S. Pat. No. 5,654,008. In the method disclosed in U.S. Pat. No. 5,654,008, a first phase, comprising the active agent and the polymer, and a second phase are pumped through a static mixer into a quench liquid to form microparticles containing the active agent. The use of a static mixer to form the emulsion tends to make the scale-up more predictable and reliable than the scale-up of other dynamic-mixing processes for making microparticles. However, numerous trials and experiments are still required to completely and accurately scale-up, such as to commercial scale or by a factor of 20 or more, a process such as the one disclosed in U.S. Pat. No. 5,654,008.
Thus, there is a need in the art for an improved method and apparatus for preparing microparticles. There is a particular need in the art for an improved process that can be more quickly, reliably, and accurately scaled-up from a laboratory or pilot scale to a commercial scale. The present invention, the description of which is fully set forth below, solves the need in the art for such a method and apparatus.
The present invention relates to an apparatus and method for preparing microparticles. In one aspect of the invention, a method of preparing microparticles is provided. The method comprises:
preparing a first phase, the first phase comprising an active agent and a polymer;
preparing a second phase;
combining the first phase and the second phase in a first static mixer to form an emulsion;
combining the emulsion and a first extraction liquid in a second static mixer; and
combining an outflow of the second static mixer with a second extraction liquid. In one aspect of such a method, the outflow of the second static mixer flows into a vessel containing the second extraction liquid. In another aspect, the outflow of the second static mixer flows into a vessel, and the second extraction liquid is added to the vessel. The second extraction liquid can be added to the vessel either while the outflow of the second static mixer is flowing into the vessel, or after the outflow of the second static mixer has completed flowing into the vessel. In yet another aspect, the outflow of the second static mixer and the second extraction liquid can be combined in another static mixer.
In a further aspect of the present invention, another method for preparing microparticles is provided. The method comprises:
preparing a first phase, the first phase comprising an active agent and a polymer;
preparing a second phase;
combining the first phase and the second phase in a first static mixer to form an emulsion, the emulsion forming an outflow of the first static mixer;
combining the outflow of the first static mixer and a first portion of a starting volume of an extraction liquid in a second static mixer to form an outflow of the second static mixer;
dividing the outflow of the second static mixer to form at least two flow streams;
flowing each of the at least two flow streams through a separate third static mixer; and
combining the at least two flow streams with a second portion of the extraction liquid.
In one aspect of such a method, the at least two flow streams flow into a vessel containing the second portion of the extraction liquid. In another aspect, the at least two flow streams and the second portion of the extraction liquid are combined in a fourth static mixer. In yet another aspect, the at least two flow streams and the second portion of the extraction liquid are combined in a fourth static mixer, and the combining step is repeated until the starting volume of the extraction liquid is depleted. The combining step may be repeated by continuing to combine the at least two flow streams and the extraction liquid in the fourth static mixer until the starting volume of the extraction liquid is depleted. Alternatively, the combining step may be repeated by combining the at least two flow streams and the extraction liquid in additional static mixers until the starting volume of the extraction liquid is depleted.
In a further aspect of the present invention, another method for preparing microparticles is provided. The method comprises:
preparing a first phase, the first phase comprising an active agent and a polymer;
preparing a second phase;
combining the first phase and the second phase in a first static mixer to form an emulsion, the emulsion forming an outflow of the first static mixer;
combining the outflow of the first static mixer and a first extraction liquid in a second static mixer to form an outflow of the second static mixer;
dividing the outflow of the second static mixer to form at least two flow streams;
flowing each of the at least two flow streams through a separate third static mixer; and
combining the at least two flow streams with a second extraction liquid.
In yet a further aspect of the present invention, a microencapsulated active agent prepared by a method for preparing microparticles is provided. Such a method comprises:
preparing a first phase, the first phase comprising an active agent and a polymer;
preparing a second phase;
combining the first phase and the second phase in a first static mixer to form an emulsion;
combining the emulsion and a first extraction liquid in a second static mixer; and
combining an outflow of the second static mixer with a second extraction liquid.
In yet a further aspect of the present invention, a microencapsulated active agent prepared by another method for preparing microparticles is provided. Such a method comprises:
preparing a first phase, the first phase comprising an active agent and a polymer;
preparing a second phase;
combining the first phase and the second phase in a first static mixer to form an emulsion, the emulsion forming an outflow of the first static mixer;
combining the outflow of the first static mixer and a first portion of a starting volume of an extraction liquid in a second static mixer to form an outflow of the second static mixer;
dividing the outflow of the second static mixer to form at least two flow streams;
flowing each of the at least two flow streams through a separate third static mixer; and
combining the at least two flow streams with a second portion of the extraction liquid.
In still a further aspect of the present invention, a system for preparing microparticles is provided. The system includes a first and second pump, and a first static mixer in fluid communication with each of the pumps. One of the pumps is configured to pump an organic phase into the first static mixer. One of the pumps is configured to pump a continuous phase into the first static mixer. A manifold, comprising a plurality of static mixers, is in fluid communication with the first static mixer. A third pump, in fluid communication with the manifold, is configured to pump an extraction liquid. A second static mixer is in fluid communication with the manifold. An outflow of the first static mixer and the extraction liquid flow through the manifold and then through the second static mixer.
In another aspect, the system can include a third static mixer in fluid communication with the first static mixer and with the manifold. The outflow of the first static mixer and the extraction liquid are combined in the third static mixer, prior to flowing through the manifold. The system may also include a vessel in fluid communication with the second static mixer so that an outflow of the second static mixer flows into the vessel. A fourth pump may also be provided to pump the extraction liquid into the second static mixer.
Features and Advantages
It is a feature of the present invention that it can be used to prepare microparticles, including microparticles containing an active agent.
It is another feature of the present invention that it allows for parallel flow streams for the in-line solvent extraction.
Yet another feature of the present invention is the ability to easily use different extraction liquids during the process. The system can be configured to introduce such different extraction liquids at the appropriate time and processing point.
An advantage of the present invention is that it substantially reduces or eliminates the need for a separate quench or extraction tank that contains a large volume of quench liquid, to remove solvent, and to form hardened microparticles.
The present invention advantageously enables the controlled extraction of the polymer solvent from a polymer/active agent droplet to form microparticles containing the active agent. The process advantageously provides a level of solvent removal sufficient for commercial products. The process also advantageously provides high loading efficiency, making it particularly useful for commercial products.
The process of the present invention advantageously provides a more consistent processing environment than conventional processes for forming microparticles. The in-line solvent extraction method of the present invention allows the emulsion droplets to all be exposed to the same processing conditions. In contrast, in conventional processes using an extraction tank or vessel, the processing conditions change over time as the solvent is extracted from the emulsion droplets in the tank.
The consistent processing conditions and environment of the present invention advantageously result in a process that is less time-dependent or scale-dependent than alternative processes.
The present invention provides a method and apparatus that are particularly advantageous for scale-up. The parallel path manifold of the present invention allows for capacity increases from an established (single path) system without full-scale trial and error experiments in new and different equipment. The total flow rate can be increased from the single path system based upon the number of flow streams in the manifold.